Thanks for the reviewing. > -----Original Message----- > From: Stephen Hemminger <step...@networkplumber.org> > Sent: Thursday, March 30, 2023 11:05 PM > To: Feifei Wang <feifei.wa...@arm.com> > Cc: dev@dpdk.org; konstantin.v.anan...@yandex.ru; > m...@smartsharesystems.com; nd <n...@arm.com> > Subject: Re: [PATCH v5 0/3] Recycle buffers from Tx to Rx > > On Thu, 30 Mar 2023 14:29:36 +0800 > Feifei Wang <feifei.wa...@arm.com> wrote: > > > Currently, the transmit side frees the buffers into the lcore cache > > and the receive side allocates buffers from the lcore cache. The > > transmit side typically frees 32 buffers resulting in 32*8=256B of > > stores to lcore cache. The receive side allocates 32 buffers and > > stores them in the receive side software ring, resulting in 32*8=256B > > of stores and 256B of load from the lcore cache. > > > > This patch proposes a mechanism to avoid freeing to/allocating from > > the lcore cache. i.e. the receive side will free the buffers from > > transmit side directly into its software ring. This will avoid the > > 256B of loads and stores introduced by the lcore cache. It also frees > > up the cache lines used by the lcore cache. And we can call this mode > > as buffer recycle mode. > > > My naive reading of this is that lcore cache update is slow on ARM so you are > introducing yet another cache. Perhaps a better solution would be to figure > out/optimize the lcore cache to work better.
>From my point of view, 'recycle buffer' is a strategic optimization. It >reduces the operation of a buffer. Not only arm, but also x86 and other architecture can benefit from this. For example, we can see x86 sse path performance improvement in cover letter test results. > > Adding another layer of abstraction is not going to help everyone and the > implementation you chose requires modifications to drivers to get it to work. > We did not change the original driver mechanism. Recycle buffer can be looked at a feature for pmd, if the user needs higher performance, he/she can choose to call the API in the application to enable it. > In current form, this is not acceptable.
